This invention relates to apparatus for controlling the temperature of lubricating oil circulating within an internal combustion engine, and more particularly concerns valve apparatus which senses the temperature of said oil and routes the oil to cooling means in response to overly high sensed temperatures.
Air-cooled gasoline-operated internal combustion engines of 4 cylinders, as used in automobiles such as the Volkswagon Beetle, generally utilize oil cooling means interposed between an oil-circulating pump and the crankshaft in a closed loop pressurized oil-circulating system. When the oil is at temperature below about 170 degrees F., it is circulated directly to the valves, bearings, and other moving parts requiring lubrication and within the circulation path of the oil. When the oil temperature rises above about 170 degrees F., an oil flow valve mechanism associated with the crankcase of the engine diverts the flow of oil to a shunt path leading through cooling coils and then back to the general oil circulation path. One reason for cooling the oil is that, at elevated temperatures, the viscosity of the oil drops to levels where it loses its lubricating characteristics; and furthermore, the elevated temperatures produce unwanted vaporization and molecular decomposition of the oil.
The conventional oil flow valve mechanisms utilized in the aforesaid engines act in accordance with pressures sensed within the oil system. In general, when the temperature of the oil rises, the pressure within the oil system decreases. Based upon such interrelationship between oil temperature and pressure, conventional oil flow valve mechanisms utilize a piston slidably positioned within a cylinder having a sealed lower portion that communicates with the engine crankcase, and an upper extremity that opens into the oil conduit line leading toward the crankshaft. By virtue of such arrangement, the piston is subjected to a differential pressure which causes it to move either upwardly toward the open extremity of the cylinder, or downwardly toward the sealed extremity. When the cylinder is in its uppermost position, in intrudes into the oil line, sealing off a path of oil flow leading directly to the crankshaft while at the same time diverting flow to an oil cooler whose output is directed toward the crankshaft.
Although said conventional oil flow valve mechanisms are of simple construction, they are not reliably accurate in controlling oil temperature because they operate indirectly based upon a pressure-sensing principle; and various engine, oil and weather factors can alter the pressure-temperature interrelationship.
U.S. Pat. No. 4,512,300 to DeVore, et al discloses an oil temperature control valve which utilizes a wax servomotor immersed in the oil being monitored and having a plunger whose axial position is dependent upon the oil temperature. When extended, the plunger is capable of closing and/or opening pathways of oil flow. However, the DeVore valve requires a very specially constructed housing and associated interactive components.
It is accordingly an object of this invention to provide apparatus for sensing and controlling the temperature of lubricating oil in an engine.
It is another object of this invention to provide apparatus as in the foregoing object readily adaptable to air cooled gasoline-operated internal combustion engines of current design.
It is a further object of the present invention to provide apparatus of the aforesaid nature of rugged and durable construction amenable to low cost manufacture.
These objects and other objects and advantages of the invention will be apparent from the following description.